<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <div id="app">
      <button @click="handler">按钮</button>
      <ul>
        <li v-for="value in arr" :key="value">{{value}}</li>
      </ul>
    </div>
    <script src="../../dist/vue.js"></script>
    <script>
      const vm = new Vue({
        el: '#app',
        data: {
          arr: ['a', 'b', 'c', 'd'],
        },
        methods: {
          handler() {
            this.arr.splice(1, 0, 'x')
          },
        },
      })

    </script>
  </body>
</html>
